Women diagnosed with breast cancer are choosing bilateral mastectomy (BLM) at increasing rates, currently 14.3%, and 33% of those under 40. This is happening despite evidence that there is no survival benefit from BLM, along with surgical complications and other serious medical and personal costs, compared with more conservative approaches. Women's anxiety about recurrence is critical to this decision, so their choice may in large part reflect the way they experience and regulate affect. To understand the neurobiological and affective determinants of the choice of BLM, and thereby identify future opportunities for new interventions, we propose to examine the relationship between affect reactivity and regulation and women's decisions regarding BLM after initial diagnosis of breast cancer. We will also examine the impact of affect management and treatment decisions on subsequent psychosocial functioning. The study will involve recruiting a sample of 150 women recently diagnosed with breast cancer after their decision about treatment (75 who have elected BLM and 75 demographically and medically similar women who have decided not to have BLM), as well as a matched control group of 50 women without breast cancer. Affective reactivity to negative non-cancer and cancer- related stimuli will be studied using functional magnetic resonance imagining (fMRI). Likewise, affective regulation will be assessed with fMRI probes of both explicit (i.e. conscious, deliberate) and implicit (i.e. nonconscious, automatic) regulation o negative non-cancer and cancer-related stimuli. Psychosocial functioning will be assessed using self-report measures of anxiety, depression, well-being and functional status at 6, 12, and 18 months post-decision. Informational (e.g. awareness of influential people who have undergone BLM), and demographic variables (age, race, SES) will also be assessed. A physiological stress response measure, diurnal salivary cortisol slope, will be obtained at baseline and all follow-ups. This measure has been shown be associated with expression of negative affect, and to predict breast cancer progression. Our Specific Aims are to: 1) Examine affect reactivity and regulation among women with a recent diagnosis of breast cancer in comparison to healthy controls; 2) Relate affect reactivity and regulation to choice of BLM; and 3) Assess long term functional consequences of BLM decision and affect reactivity and regulation. This study will provide an empirical basis for better assisting patients in making difficult but important choices regarding breast cancer treatment alternatives.